Pin type grippers that employ a combination of substantially straight pins and cooperating domes have been used successfully in case opening systems for corrugated boxes many years. Corrugated boxes are boxes generally make from corrugated board composed of a pair of outer liner with a corrugated medium there between. The corrugated medium connects and holds the liners in substantially parallel spaced relationship. These pin type gripper systems rely on a series of pins that are carefully aligned with domes and that penetrate the open end of panels (flaps) on the corrugated box (i.e. between the liners) in a direction parallel to the longitudinal axis of the corrugations in the medium. The pins combine with their respective adjacent domes to grip the liner there between.
Attention is directed to U.S. Pat. No. 4,553,954 issued Nov. 19, 1985 Sewell et al. which shows a known pin and dome systems and applies it in known manner to grip adjacent panels of a corrugated box and then move them to squared position i.e. at right angles to each other to in effect open the case as part of the case erection process.
One of the major complains about these known systems that has subsisted over the years is the difficulty in adjusting the grippers to accommodate different type of corrugated material from which the boxes may be made. These adjustments are currently achieved in two different ways namely by adjusting the clearance between the pins and their respective adjacent domes or by adding or subtracting to change the total number of pins being employed.
Adjusting the clearance is obtained by removing the pin blocks which are formed with the longitudinal axis of the pins closed to one mounting surface than the opposite mounting surface and flipping the pin blocks and reattaching them so that the position (spacing) of the pins from the surface on which the pins and domes are mounted is changed. In the known systems this is a time consuming process in that it requires the use of tools to remove the pin blocks and requires time to ensure that when the blocks are reassembled in the apparatus they are correctly aligned
Changing the number of pins for reducing the number of pins requires removal of the set screws that hold each individual pin to be removed in its mounting block and removing the pin. Increasing the number of pins requires positioning the additional pin(s) and inserting and tightening the clamping set screw to clamp the added pin in position. If a set screw was already in place it must at least be loosened the pin inserted and then tightened so that the set screw holds the new pin in place.
Even when the pins are properly inserted there are occasions where slippage is incurred which on occasion results in the case moving relative to the jaws during the squaring operation